Scrutinizing the Delta Cross Channel

CALFED | June 1st, 2001

Sea Level Rise Impacts on Wastewater Treatment Systems Along the U.S. Coasts

American Geophysical Union (AGU) | April 13th, 2018

Wastewater treatment plants are susceptible to flooding resulting from sea level rise. Previous estimates of wastewater exposure have only considered the impacts of mar

Wastewater treatment plants are susceptible to flooding resulting from sea level rise. Previous estimates of wastewater exposure have only considered the impacts of marine flooding at the local or regional scale. In this analysis, we quantify the exposure to marine flooding across the coastal United States and then consider the relative impacts of marine and groundwater flooding at the regional scale in the San Francisco Bay Area. We also estimate the number of people who may lose access to wastewater services if no actions are taken to prevent flooding at wastewater treatment plants. We find that the number of people impacted by sea level rise due to loss of wastewater services could be five times as high as previous predictions of the number of people who experience direct flooding of their homes or property. We also find that groundwater flooding poses a significant threat to wastewater plants in the San Francisco Bay region.

Sea-level rise and coastal groundwater inundation and shoaling at select sites in California, USA

Journal of Hydrology: Regional Studies (Elsevier) | January 5th, 2016

Study region: The study region spans coastal California, USA, and focuses on three primary sites: Arcata, Stinson Beach, and Malibu Lagoon. Study focus: 1m and 2m sea-

Study region: The study region spans coastal California, USA, and focuses on three primary sites: Arcata, Stinson Beach, and Malibu Lagoon. Study focus: 1m and 2m sea-level rise (SLR) projections were used to assess vulnerability to SLR-driven groundwater emergence and shoaling at select low-lying, coastal sites in California. Separate and combined inundation scenarios for SLR and groundwater emergence were developed using digital elevation models of study site topography and groundwater surfaces constructed from well data or published groundwater level contours. New hydrological insights for the region: SLR impacts are a serious concern in coastal California which has a long (∼1800km) and populous coastline. Information on the possible importance of SLR-driven groundwater inundation in California is limited. In this study,the potential for SLR-driven groundwater inundation at three sites (Arcata, Stinson Beach,and Malibu Lagoon) was investigated under 1m and 2m SLR scenarios. These sites provide insight into the vulnerability of Northern California coastal plains, coastal developments built on beach sand or sand spits, and developed areas around coastal lagoons associated with seasonal streams and berms. Northern California coastal plains with abundant shallow groundwater likely will see significant and widespread groundwater emergence, while impacts along the much drier central and southern California coast may be less severe due to the absence of shallow groundwater in many areas. Vulnerability analysis is hampered by the lack of data on shallow coastal aquifers, which commonly are not studied because they are not suitable for domestic or agricultural use. Shallow saline aquifers may be present in many areas along coastal California, which would dramatically increase vulnerability to SLR-driven groundwater emergence and shoaling. Improved understanding of the extent and response of California coastal aquifers to SLR will help in preparing for mitigation and adaptation.

Sea-level rise impacts on seawater intrusion in coastal aquifers: Review and integration

Journal of Hydrology (Elsevier) | February 6th, 2016

Sea-level rise (SLR) influences groundwater hydraulics and in particular seawater intrusion (SWI) in many coastal aquifers. The quantification of the combined and relativ

Sea-level rise (SLR) influences groundwater hydraulics and in particular seawater intrusion (SWI) in many coastal aquifers. The quantification of the combined and relative impacts of influential factors on SWI has not previously been considered in coastal aquifers. In the present study, a systematic review of the available literature on this topic is first provided. Then, the potential remaining challenges are scrutinized. Open questions on the effects of more realistic complexities such as gradual SLR, parameter uncertainties, and the associated influences in decision-making models are issues requiring further investigation. We assess and quantify the seawater toe location under the impacts of SLR in combination with recharge rate variations, land-surface inundation (LSI) due to SLR, aquifer bed slope variation, and changing landward boundary conditions (LWBCs). This is the first study to include all of these factors in a single analysis framework. Both analytical and numerical models are used for these sensitivity assessments. It is demonstrated that (1) LSI caused by SLR has a significant incremental impact on the seawater toe location, especially in the flatter coasts and the flux-controlled (FC) LWBCs, however this impact is less than the reported orders of magnitude differences which were estimated using only analytical solutions; (2) LWBCs significantly influence the SLR impacts under almost all conditions considered in this study; (3) The main controlling factors of seawater toe location are the magnitudes of fresh groundwater discharge to sea and recharge rate. Regional freshwater flux entering from the landward boundary and the groundwater hydraulic gradient are the major contributors of fresh groundwater discharge to sea for both FC and head-controlled (HC) systems, respectively; (4) A larger response of the aquifer and larger seawater toe location changes are demonstrable for a larger ratio of the aquifer thickness to the aquifer length particularly in the HC systems; (5) The lowest sensitivity of seawater toe location is found for the density difference ratio of the seawater and freshwater, and also for the aquifer bed slope; (6) The early-time observations show seawater fingers below the inundated lands due to SLR which are diminished and ultimately extinguished; and (7) A less than 2% reversal effect on the seawater toe location after overshoot mechanism is observed in the transient simulations which suggests that this mechanism is an insignificant and impractical factor compared to other more significant factors.

Seawater Intrusion in a Coastal California Aquifer

U.S. Geological Survey (USGS) | July 18th, 1996

Seawater intrusion in aquifers underlying the Oxnard Plain, Ventura County, California, was first observed in the early 1930's and became a serious problem in the mid-195

Seawater intrusion in aquifers underlying the Oxnard Plain, Ventura County, California, was first observed in the early 1930's and became a serious problem in the mid-1950's (California Department of Water Resources, 1965) (fig. 1). Historically, local agencies responsible for the management of ground water used a criterion of 100 milligrams per liter (mg/L) chloride to define the leading edge of the seawater front. It was assumed that all high-chloride water from wells behind the front originated from seawater that entered aquifers through outcrop areas in submarine canyons. Recent work (Izbicki, 1991; Stamos and others, 1992) showed that other sources of high-chloride water to wells are present and that the areal extent of seawater intrusion in the upper aquifer system is smaller than previously believed.

Seawater intrusion processes, investigation and management: Recent advances and future challenges

Advances in Water Resources (Elsevier) | January 17th, 2013

Seawater intrusion (SI) is a global issue, exacerbated by increasing demands for freshwater in coastal zones and predisposed to the influences of rising sea levels and ch

Seawater intrusion (SI) is a global issue, exacerbated by increasing demands for freshwater in coastal zones and predisposed to the influences of rising sea levels and changing climates. This review presents the state of knowledge in SI research, compares classes of methods for assessing and managing SI, and suggests areas for future research. We subdivide SI research into categories relating to processes, measurement, prediction and management. Considerable research effort spanning more than 50 years has provided an extensive array of field, laboratory and computer-based techniques for SI investigation. Despite this, knowledge gaps exist in SI process understanding, in particular associated with transient SI processes and timeframes, and the characterization and prediction of freshwater–saltwater interfaces over regional scales and in highly heterogeneous and dynamic settings. Multidisciplinary research is warranted to evaluate interactions between SI and submarine groundwater discharge, ecosystem health and unsaturated zone processes. Recent advances in numerical simulation, calibration and optimization techniques require rigorous field-scale application to contemporary issues of climate change, sea-level rise, and socioeconomic and ecological factors that are inseparable elements of SI management. The number of well-characterized examples of SI is small, and this has impeded understanding of field-scale processes, such as those controlling mixing zones, saltwater upconing, heterogeneity effects and other factors. Current SI process understanding is based mainly on numerical simulation and laboratory sand-tank experimentation to unravel the combined effects of tides, surface water–groundwater interaction, heterogeneity, pumping and density contrasts. The research effort would benefit from intensive measurement campaigns to delineate accurately interfaces and their movement in response to real-world coastal aquifer stresses, encompassing a range of geological and hydrological settings.

Second Report of Recharge Parties Pursuant to RWQCB Resolution No. R8-2008-0019 Cooperative Agreement to Protect Water Quality and Encourage the Conjunctive Uses of Imported Water in the Santa Ana River Basin, Yucaipa and San Timoteo Management Zones

San Bernardino Valley Municipal Water District | July 18th, 2012

The importation of water (i.e., State Water Project (SWP) water, Colorado River water, and imported groundwater) to groundwater basins within the Santa Ana River Region

The importation of water (i.e., State Water Project (SWP) water, Colorado River water, and imported groundwater) to groundwater basins within the Santa Ana River Region is necessary to meet increasing demand. However, long-term conjunctive use of water within the Region could affect groundwater quality. As such, the California Regional Water Quality Control Board Santa Ana Region (RWQCB) is requiring that groundwater quality be managed to meet the water quality objectives for total dissolved solids (TDS) and nitrogen (i.e., Salinity Objectives) regulated in the 1995 Water Quality Control Plan for the Santa Ana River Basin (Basin Plan). On January 22, 2004, the RWQCB adopted Resolution No. R8-2004-0001, incorporating an updated TDS and nitrogen management plan that includes revised groundwater subbasin boundaries; revised TDS and nitrate-nitrogen water quality objectives for groundwater; revised TDS and nitrogen waste load allocations; and revised reach designations, TDS and nitrogen objectives and beneficial uses for specific surface waters. On May 19, 2006, the RWQCB considered a resolution and order that would have adopted general waste discharge requirements for the recharge of imported water to the Santa Ana River Basin. Based on input from stakeholders, it was decided by the RWQCB that the feasibility of a cooperative program should be investigated that would achieve the objectives of and obviate the adoption of the draft resolution and order under consideration. On January 18, 2008, the RWQCB adopted Resolution No. R8-2008-0019 authorizing a “Cooperative Agreement to Protect Water Quality and Encourage the Conjunctive Use of Imported Water in the Santa Ana River Basin.” The purpose of the cooperative agreement is to allow the participating parties to “…monitor and improve water quality objectives within the Santa Ana River Region in a manner that is consistent with the needs of the inhabitants of the Region for a reliable supply of water.” (Cooperative Agreement, 2008). The following Parties have entered into this cooperative agreement: California Regional Water Quality Control Board, Santa Ana Region, City of Corona, City of Riverside, City of San Bernardino Municipal Water Department, Eastern Municipal Water District, Elsinore Valley Municipal Water District, Orange County Water District, San Bernardino Valley Municipal Water District (Valley District), San Gorgonio Pass Water Agency, and Western Municipal Water District of Riverside County (Western).  

Sediment Management (Resource Management Strategy)

California Department of Water Resources (DWR) | July 29th, 2016

Sediment in California is a valuable resource when it is properly managed, which results in multiple water benefits, environmental health, economic stability, and coastal

Sediment in California is a valuable resource when it is properly managed, which results in multiple water benefits, environmental health, economic stability, and coastal safety. Sediment definitions vary among the professional disciplines. Sediment, as reflected in this resource management strategy report, is composed of natural materials and used contextually as follows: 1. Geology considers sediment to be the solid fragmented material, such as silt, sand, gravel, chemical precipitates, and fossil fragments, which has been transported and deposited by water, ice, or wind, or that accumulates through chemical precipitation or secretion by organisms, and that forms layers on the Earth’s surface. Sedimentary rocks consist of consolidated sediment. 2. The U.S. Environmental Protection Agency (EPA) and U.S. Army Corps of Engineers (USACE) regard sediment as material, such as sand, silt, or clay, suspended in or settled on the bottom of a water body. Sediments can come from anywhere and be just about anything. Organic and inorganic material alike can become bits of matter tiny enough to be picked up and carried along with a moving fluid. Organic sediments are made up of mostly plant and animal debris. Inorganic sediments are divided into two main groups — coarse-grained sediments and fine-grained sediments. Coarse- grained sediments are boulders, cobbles, gravel, and sand. Fine-grained sediments are silts and clays. Sediment deposits, like tree rings, can serve as a record of natural history. A further important distinction is whether they are clean sediments or contaminated sediments, as this greatly affects the manner in which they can be used as beneficial material or if they must be isolated from their surrounding environment.

Sediment Supply to San Francisco Bay, Water Years 1995 through 2016: Data, trends, and monitoring recommendations to support decisions about water quality, tidal wetlands, and resilience to sea level rise

San Francisco Estuary Institute (SFEI) | June 11th, 2018

Knowledge of the status and trends of sediment supply to San Francisco Bay is critically important for management decisions about dredging, marsh restoration, flood contr

Knowledge of the status and trends of sediment supply to San Francisco Bay is critically important for management decisions about dredging, marsh restoration, flood control, contaminants, water clarity (in relation to primary production), and sea level rise. Several site-specific studies of sediment supply to San Francisco Bay have been conducted, but no synthesis of recent studies is available. The purpose of this report is to synthesize the best available data and knowledge to answer a few of the key study questions related to sediment supply to the Bay (listed below). This synthesis report was prepared jointly by the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) and the U. S. Geological Survey (USGS) with funding from both organizations. The project is meant to be a step in the development of a more comprehensive sediment management and monitoring strategy for the Bay.

Sediment Supply to San Francisco Bay, Water Years 1995 through 2016: Data, trends, and monitoring recommendations to support decisions about water quality, tidal wetlands, and resilience to sea level rise

San Francisco Estuary Institute (SFEI) | June 11th, 2018

Knowledge of the status and trends of sediment supply to San Francisco Bay is critically important for management decisions about dredging, marsh restoration, flood contr

Knowledge of the status and trends of sediment supply to San Francisco Bay is critically important for management decisions about dredging, marsh restoration, flood control, contaminants, water clarity (in relation to primary production), and sea level rise. Several site-specific studies of sediment supply to San Francisco Bay have been conducted, but no synthesis of recent studies is available. The purpose of this report is to synthesize the best available data and knowledge to answer a few of the key study questions related to sediment supply to the Bay.  This synthesis report was prepared jointly by the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) and the U. S. Geological Survey (USGS) with funding from both organizations. The project is meant to be a step in the development of a more comprehensive sediment management and monitoring strategy for the Bay.